E3 Standard correction factors for intermittent shading using various glass/blind combinations are given in Table E1. Where available shading coefficient data for a particular device should be used to calculate the correction factor, in preference to using the figures given in Table E1. The correction factor is calculated as follows: (a) For fixed shading (including units with absorbing or reflecting glass), the correction factor (fc) is given by fc = Sc/0.7 (b) For moveable shading, the correction factor is given by fc = 0.5(1 + (Sc/0.7)) where Sc is the shading coefficient for the glazing/shading device combination, i.e. the ratio of the instantaneous heat gain at normal incidence by the glazing/shading combination relative to the instantaneous heat gain by a sheet of 4 mm clear glass (c) Where there is a combination of fixed and moveable shading, the correction factor is given by fc = (Scf + Sctot)/1.4 where Scf is the shading coefficient of the fixed shading (with glazing) and Sctot is the shading coefficient of the combination of glazing and fixed and moveable shading.

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E3 Standard correction factors for intermittent shading using various glass/blind combinations are given in Table E1. Where available shading coefficient data for a particular device should be used to calculate the correction factor, in preference to using the figures given in Table E1. The correction factor is calculated as follows: (a) For fixed shading (including units with absorbing or reflecting glass), the correction factor (fc) is given by fc = Sc/0.7 (b) For moveable shading, the correction factor is given by fc = 0.5(1 + (Sc/0.7)) where Sc is the shading coefficient for the glazing/shading device combination, i.e. the ratio of the instantaneous heat gain at normal incidence by the glazing/shading combination relative to the instantaneous heat gain by a sheet of 4 mm clear glass (c) Where there is a combination of fixed and moveable shading, the correction factor is given by fc = (Scf + Sctot)/1.4 where Scf is the shading coefficient of the fixed shading (with glazing) and Sctot is the shading coefficient of the combination of glazing and fixed and moveable shading.

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Example E1 E4 A school classroom is 9 m long by 6 m deep, with a floor to ceiling height of 2.9 m. There is glazing on one wall, with rooflights along the internal wall opposite the window wall. The windows are 1200 mm wide by 1000 mm high, and there are six such windows in the external wall, which faces SE. The windows are clear double glazed, with mid-pane blinds, of wooden frames with a framing percentage of 25%. There are three 0.9 m2 horizontal rooflights, with an internal blind and low-e glass on the inner pane of the double pane unit. Is there likely to be a solar overheating problem? (a) As the room is not more than 6 m deep, it should be considered as a single “perimeter zone” – there is no “interior zone” (b) The calculation of the average solar cooling load (W) is set out in the following Table. (c) the total average solar cooling load per unit floor area (W/m2) is derived by dividing the total average solar load by the zone floor area. In this case the floor area is 54 m2 and the total average solar cooling load per unit floor area is 24.20 (W/m2). As this is less than 25 W/m2, there is not likely to be an overheating problem.

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Example E2 E5 An office building has a floor to ceiling height of 2.8 m and curtain walling construction with a glazing ratio of 0.6. The long side of the office faces south and the short side faces west. On each floor, the main office area is open plan, but there is a 5 m by 3 m corner office, with the 5 m side facing South. It is proposed to use double glazing with the internal pane low-e glazing and the external pane absorbing glass, and with an internal blind. For the open plan areas, the perimeter zone is defined by the 6 m depth rule, but for the corner office, it is defined by the partitions. The glazed area is taken as the nominal area less 10% for framing. Three different situations must be considered – the south facing open plan area; – the west facing open plan area; and – the corner office. Open plan area From Table 7, it can be seen that the solar loading for a West orientation (205 W/m2) exceeds that for a South orientation (156 W/m2). Thus, on the assumption that the same construction would be used on West and South facades, it is sufficient to check the West orientation for the open plan offices. For a typical 5 m length of West facing office, the floor area of the perimeter zone is 30 m2, and the area of glazing is 7.56 m2, i.e. width (5 m) x height (2.8 m) x glazing ratio (0.6) x framing correction (0.9). The glazing/blind correction factor is 0.62 and the solar loading is 205 W/m2. Thus the total average solar cooling load per unit floor area (W/m2) is (7.56 x .62 x 205)/30 = 32W/m2. As this is greater than the threshold of 25 W/m2, it is necessary to decrease the glazing ratio or provide alternative or additional shading devices, e.g. a reduction in glazing ratio to 0.47 or provision of fixed shading devices which would provide a shading coefficient of 0.34 (giving a correction factor of 0.43), or a combination of these measures would reduce the risk of solar overheating to acceptable levels. Corner Office For the purpose of this example, it is assumed that it has been decided to reduce the glazing ratio of the building to 0.47. On this basis the average solar load for this office can be calculated as set out in the following table. The office floor area is 15 m2 and the total average solar cooling load per unit floor area (W/m2) is 68 W/m2. To achieve a total average solar cooling load per unit floor area (W/m2) of 25 W/m2 would require a reduction in the total average solar load to 375 W. This can be achieved by a further reduction of glazing area, e.g. through the use of opaque panels so as to reduce the glazing ratio for the corner office to 17%. An alternative would be to use external shading devices to give a correction factor of 0.22. This implies fixed shading with a shading coefficient of 0.16. Such a shading coefficient is quite demanding to achieve in practice. Alternatively a more detailed calculation could be undertaken. If the corner office was not partitioned from a general open floor area, it’s solar load could be considered as part of the load of one of the facades it shares

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Example E2 E5 An office building has a floor to ceiling height of 2.8 m and curtain walling construction with a glazing ratio of 0.6. The long side of the office faces south and the short side faces west. On each floor, the main office area is open plan, but there is a 5 m by 3 m corner office, with the 5 m side facing South. It is proposed to use double glazing with the internal pane low-e glazing and the external pane absorbing glass, and with an internal blind. For the open plan areas, the perimeter zone is defined by the 6 m depth rule, but for the corner office, it is defined by the partitions. The glazed area is taken as the nominal area less 10% for framing. Three different situations must be considered – the south facing open plan area; – the west facing open plan area; and – the corner office. Open plan area From Table 7, it can be seen that the solar loading for a West orientation (205 W/m2) exceeds that for a South orientation (156 W/m2). Thus, on the assumption that the same construction would be used on West and South facades, it is sufficient to check the West orientation for the open plan offices. For a typical 5 m length of West facing office, the floor area of the perimeter zone is 30 m2, and the area of glazing is 7.56 m2, i.e. width (5 m) x height (2.8 m) x glazing ratio (0.6) x framing correction (0.9). The glazing/blind correction factor is 0.62 and the solar loading is 205 W/m2. Thus the total average solar cooling load per unit floor area (W/m2) is (7.56 x .62 x 205)/30 = 32W/m2. As this is greater than the threshold of 25 W/m2, it is necessary to decrease the glazing ratio or provide alternative or additional shading devices, e.g. a reduction in glazing ratio to 0.47 or provision of fixed shading devices which would provide a shading coefficient of 0.34 (giving a correction factor of 0.43), or a combination of these measures would reduce the risk of solar overheating to acceptable levels. Corner Office For the purpose of this example, it is assumed that it has been decided to reduce the glazing ratio of the building to 0.47. On this basis the average solar load for this office can be calculated as set out in the following table. The office floor area is 15 m2 and the total average solar cooling load per unit floor area (W/m2) is 68 W/m2. To achieve a total average solar cooling load per unit floor area (W/m2) of 25 W/m2 would require a reduction in the total average solar load to 375 W. This can be achieved by a further reduction of glazing area, e.g. through the use of opaque panels so as to reduce the glazing ratio for the corner office to 17%. An alternative would be to use external shading devices to give a correction factor of 0.22. This implies fixed shading with a shading coefficient of 0.16. Such a shading coefficient is quite demanding to achieve in practice. Alternatively a more detailed calculation could be undertaken. If the corner office was not partitioned from a general open floor area, it’s solar load could be considered as part of the load of one of the facades it shares

Standards and Other References Standards referred to: I.S. 161: 1975 Copper direct cylinders for domestic purposes. I.S. 325-1: 1986 Code of Practice for use of masonry – part 1: Structural use of unreinforced masonry. I.S. EN 1745: 2002 Masonry And Masonry Products – Methods for determining Design Thermal Values. I.S. EN ISO 6946: 1997 Building components and building elements –Thermal resistance and thermal transmittance – Calculation method Amd 1 2003. I.S. EN ISO 8990: 1997 Thermal insulation – Determination of steady-state thermal transmission properties – Calibrated and guarded hot box. I.S. EN ISO 10077-1: 2001 Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: simplified method. I.S. EN 10077-2: 2000 Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 2: Numerical methods for frames. I.S. EN ISO 10211-1: 1996 Thermal bridges in building construction – heat flows and surface temperatures. Part 1 general calculation methods. I.S. EN ISO 10211-2: 2001 Thermal bridges in building construction – heat flows and surface temperatures. Part 2 linear thermal bridges. I.S. EN ISO 10456: 2000 Building materials and products – procedures for determining declared and design thermal values. I.S. EN 12524: 2000 Building materials and products – Hygrothermal properties – Tabulated design values. I.S. EN ISO 12567-1: 2001 Thermal performance of windows and doors – Determination of thermal transmittance by hot box method – Part 1: Complete windows and doors. I.S. EN ISO 13370: 1999 Thermal performance of buildings – Heat transfer via the ground – Calculation methods. I.S. EN ISO 13789: 2000 Thermal Performance of Buildings – Transmission Heat Loss Coefficient – Calculation Method. I.S. EN 13829: 2000 Thermal Performance of Buildings: Determination of air permeability of buildings: fan pressurisation method. BS 747: 2000 Reinforced bitumen sheets for roofing – Specification. BS 1566 Part 1: 2002 Copper indirect cylinders for domestic purposes, open vented copper cylinders. Requirements and test methods. BS 5422 : 2001 Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment (operating within the temperature range – 400C to + 7000C). BS 8206 Part 2: 1992 Lighting for buildings. Code of practice for daylighting. Other Publications referred to: BRE Digest 465, U-values for light steel frame construction, BRE, 2002. BRE Information Paper 1/06 Assessing the effects of thermal bridging at junctions and around openings, BRE, 2001. BRE Information Paper 10/02, Metal cladding: assessing the thermal performance of built-up systems using ‘Z’ spacers, BRE, 2002 BRE Information Paper 1/06 Assessing the affects of thermal bridging at junctions and around openings, BRE 2006 BRE Report BR 262, Thermal Insulation: avoiding risks, BRE, 2001 BRE Report BR 364, Solar shading of buildings, BRE, 1999 BRE Report BR 443, Conventions for U-value Calculations, BRE, 2002. BRE Report BR 497, Conventions for calculating linear thermal transmittance and temperature factors, BRE, 2007 CIBSE Guide A: Environmental Design – Section 3: Thermal Properties of Buildings and Components, CIBSE, 1999 CIBSE TM 23: Testing Buildings for Air Leakage, CIBSE, 2000 Chris Knights and Nigel Potter, Airtightness Testing for New Dwellings, A BSRIA Guide ,BSRIA, 2006 DEHLG, Limiting Thermal Bridging and Air Infiltration – Acceptable Construction Details availabe on www.environ.ie Domestic Energy Assessment Procedure (DEAP) SEI 2006 (www.sei.ie) Good Practice Guide 268, Energy efficient ventilation in dwellings – a guide for specifiers, 2006 Home-heating Appliance Register of Performance (HARP) database, SEI (www.sei.ie/harp). Heating and Domestic Hot Water Systems for dwellings – Achieving compliance with Part L. MCRMA Technical Paper No. 14, Guidance for the

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Example A4: Slab-on-ground floor – full floor insulation The slab-on-ground floor consists of a 150 40 mm dense concrete ground floor slab on 100 mm insulation. The insulation has a thermal conductivity of 0.031 W/mK. The floor dimensions are 8750 mm by 7250 mm with three sides exposed. One 8750 mm side abuts the floor of an adjoining semi-detached house. In accordance with I.S. EN ISO 13370: 2007, the following expression gives the U-value for well-insulated floors: – U = /(0.457B’ + dt), where = thermal conductivity of unfrozen ground (W/mK) B’ = 2A/P (m) dt = w + (Rsi + Rf + Rse) (m) A = floor area (m2) P = heat loss perimeter (m) w = wall thickness (m) Rsi, Rf and Rse are internal surface resistance, floor construction (including insulation) resistance and external surface resistance respectively. Standard values of Rsi and Rse for floors are given as 0.17 m2K/W and 0.04 m2K/W respectively. The standard also states that the thermal resistance of dense concrete slabs and thin floor coverings may be ignored in the calculation and that the thermal conductivity of the ground should be taken as 2.0 W/mK unless otherwise known or specified. Ignoring the thermal resistance of the dense concrete slab, the thermal resistance of the floor construction (Rf) is equal to the thermal resistance of the insulation alone, i.e. 0.1 / 0.031 or 3.226 m2K/W. Taking the wall thickness as 350 mm, this gives: – dt = 0.35 + 2.0(0.17 + 3.226 + 0.04) = 7.222 m Also B’ = 2(8.75 x 7.25) / (8.75 + 7.25 + 7.25) = 5.457 m Therefore U = 2.0 / ((0.457 x 5.457) + 7.222) = 0.21 W/m2K The edge insulation to the slab is provided to prevent thermal bridging at the edge of the slab. I.S. EN ISO 13370: 2007 does not consider this edge insulation as contributing to the overall floor insulation and thus reducing the floor U-value. However, edge insulation, which extends below the external ground level, is considered to contribute to a reduction in floor U-value and a method of taking this into account is included in the standard. Foundation walls of insulating lightweight concrete may be taken as edge insulation for this purpose.

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E1 This Appendix provides the detail for the procedure referred to in paragraph 1.2.6.2 (a).

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E1 This Appendix provides the detail for the procedure referred to in paragraph 1.2.6.2 (a).

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E2 When estimating the solar load, the space being considered should be split into perimeter and interior zones. “Perimeter zones” are those defined by a boundary drawn a maximum of 6 m away from the window wall(s). Interior zones are defined by the space between this perimeter boundary and the nonwindow walls or the perimeter boundary of another perimeter zone. When calculating the average solar cooling load, the contribution from all windows within that zone should be included, plus the contribution from any rooflight (or part rooflight) that is within the zone boundary. For interior zones, the contribution from all rooflights (or part rooflights) that is within its zone boundary should be included. For each zone within the space, the total average solar cooling load per unit floor area should be no greater than 25 W/m2. The total average solar cooling load per unit floor area (W/m2) is calculated as follows: – The average solar cooling load associated with each glazed area is calculated by multiplying the area of glazing by the solar load for the appropriate orientation (see Table 7) and by a correction factor applicable to the relevant glazing/blind combination (see Paragraph E3 and Table E1); – The average solar cooling loads thus calculated are added together and the sum divided by the zone floor area to give a total average solar cooling load per unit floor area (W/m2). Where the actual glazed area is not known, it can be assumed to equate to the opening area reduced by an allowance for framing. The default reduction should be taken as 10% for windows and 30% for rooflights.

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